This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-335089, filed Nov. 1, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
This invention relates to a color ink-jet head to be suitably used for a printing machine, a copying machine, a facsimile set, a plotter or the like.
2. Description of the Related Art
The ink-jet printing technology is being popularly used for color printing machines because it facilitates color printing. In recent years, the number of nozzles of color printing machine for ejecting ink droplets has been increased remarkably to meet the demand for high resolution and high speed printing. Accordingly, large ink-jet heads provided with a huge number of nozzles have been developed. However, such complex ink-jet heads entails a poor manufacturing yield and hence is costly. Thus, efforts have been paid to develop ink-jet heads comprising a plurality of head units, each having a relatively small number of nozzles in an attempt at reducing the manufacturing cost. For instance, a color ink-jet head can be produced by preparing large head blocks, each comprising a plurality of head units having relatively small number of nozzles, and arranging as many head blocks as the number of ink colors to be used for the ink-jet head. Such a color ink-jet head operates just like a color ink-jet head formed by arranging as many large heads as the number of ink colors to be used for the color ink-jet head.
Meanwhile, there are low speed machines, standard speed machines and high speed machines comprising a color ink-jet head. Of these, low speed printing machines use only a small number of nozzles, whereas high speed printing machines requires a large number of nozzles so that a large number of pixels may be produced by each printing operation, which needs to be conducted at high speed.
Conventionally, low speed machines, standard speed machines and high speed machines are realized either by differentiating the head lengths as shown in FIGS. 14A, 14B and 14C of the accompanying drawing or by differentiating the number of head units, or using head blocks with different lengths, as shown in FIGS. 15A, 15B and 15C of the accompanying drawing. Note that, in FIGS. 14A through 15C, reference symbol B denotes a head unit using black ink and reference symbol Y denotes a head unit using yellow ink, while reference symbols M and C respectively denote a head unit using magenta ink and a head unit using cyan ink.
However, the head units of the machines shown in FIGS. 14A through 14C have respective heads with a length differentiated for the low speed machine, the standard speed machine and the high speed machine. In other words, low speed machines, standard speed machines and high speed machines require manufacture of respective dedicated heads, which is an operation entailing a low economic efficiency and a high manufacturing cost. Similarly, in the case of printing machines adapted to use head blocks, different dedicated head blocks as shown in FIGS. 15A through 15C have to be prepared for the low speed machine, the standard speed machine and the high speed machine. The net result will also be a low economic efficiency and a high manufacturing cost.
The problem of low economic efficiency and high cost also arises when the number of heads is doubled for the low speed machine, the standard speed machine and the high speed machine in such a way that the nozzles of one of the head groups and those of the other head group are arranged alternately to halve the pitch of nozzle arrangement and double the resolution because the number of dedicated heads or head blocks have to be increased for each of the low speed machine, the standard speed machine and the high speed machine.
In view of the above identified circumstances, it is therefore the object of the present invention to provide a color ink-jet head that can be realized by using a plurality of identical head blocks regardless if it is used for a high speed machine, a standard speed machine or a low speed machine to consequently raise the economic efficiency and lower the cost.
According to one aspect of the present invention, the above object is achieved by providing a color ink-jet head comprising: a plurality of head units each having 1/n of a total number of nozzles predetermined as a maximum number to jet ink of one color in one scanning, where n is an integer equal to or greater than 2, and wherein the nozzles of each of the head units are arranged at a same pitch; and a plurality of head blocks each having at least as many said head units as a number of different ink colors to be used for the ink-jet head. The head units are provided for holding respective inks of the different ink colors and are arranged in a direction perpendicular to a printing direction of the ink-jet head. A predetermined number of said head blocks are arranged in the printing direction in such a manner that no head units of a same color are aligned in the printing direction, and said head blocks execute printing for said predetermined number of head blocks multiplied by 1/n of a printing width in one scanning.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description given above or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.